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I recently purchased a set of CTR-301P flash triggers from ebay. I was happy that they triggered my studio flashes but disappointed that they did not fire my Promaster hot shoe flash. I did some searching and found that others had added a wire from the hot shoe ground to the battery ground but this did not solve the problem for me.
I decided that I needed to figure out what the difference was between the triggers and the camera hot shoe. I disassembled one of the triggers and the transmitter and measured the trigger pulse of the camera and the trigger pulse of the flash trigger. What I found was that the flash triggers pulse did not drop all the way to zero volts like the camera flash did, it always dropped to two. This is due to a rectifier bridge that was placed in line between the shoe connector and the switching transistor. Looking up the data sheet for the bridge revealed a forward voltage of 1v for each diode. Eureka! I decided to move the hot shoe to the DC side of the rectifier and leave the PC connector on the AC side to maintain the safety that was designed in for AC studio flashes.
You'll need a fine tip soldering iron and the skills to use it, some fine gauge solid copper wire and a black or red marker.
Read on to see how I modified the triggers to eliminate the 2v drop.
Disclaimer: This worked for me and it should work for you. If you do not have experience soldering small surface mount components this is not the project to learn on. If you attempt this and blow up hundreds or dollars in photo equipment, I'm sorry for your loss but you should have spent the money for pocket wizards or radio poppers instead of hacking ebay triggers.
I decided that I needed to figure out what the difference was between the triggers and the camera hot shoe. I disassembled one of the triggers and the transmitter and measured the trigger pulse of the camera and the trigger pulse of the flash trigger. What I found was that the flash triggers pulse did not drop all the way to zero volts like the camera flash did, it always dropped to two. This is due to a rectifier bridge that was placed in line between the shoe connector and the switching transistor. Looking up the data sheet for the bridge revealed a forward voltage of 1v for each diode. Eureka! I decided to move the hot shoe to the DC side of the rectifier and leave the PC connector on the AC side to maintain the safety that was designed in for AC studio flashes.
You'll need a fine tip soldering iron and the skills to use it, some fine gauge solid copper wire and a black or red marker.
Read on to see how I modified the triggers to eliminate the 2v drop.
Disclaimer: This worked for me and it should work for you. If you do not have experience soldering small surface mount components this is not the project to learn on. If you attempt this and blow up hundreds or dollars in photo equipment, I'm sorry for your loss but you should have spent the money for pocket wizards or radio poppers instead of hacking ebay triggers.
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Signing UpStep 1Disassemble the trigger
First remove the battery from the trigger.
Then remove the 4 screws from the bottom.
Gently pull apart the two cases. The label on the end where the switch is located is attached with double sided tape. Pull gently and it will come off. Be careful not to pull too hard on the wires that connect the hot shoe to the circuit board.
Gently pull the hot shoe connector from the circuit board.
Now remove the two small phillips screws that hold the circuit board to the case.
The board should pull out easily now.
Then remove the 4 screws from the bottom.
Gently pull apart the two cases. The label on the end where the switch is located is attached with double sided tape. Pull gently and it will come off. Be careful not to pull too hard on the wires that connect the hot shoe to the circuit board.
Gently pull the hot shoe connector from the circuit board.
Now remove the two small phillips screws that hold the circuit board to the case.
The board should pull out easily now.
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Nov 24, 2010. 4:19 PMTobeFFM
says:
hi! sadly not even that helped me fire my canon speedlite 188a (3,5V trigger voltage)....
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